Radiological criteria for a mass lesion are:  Lateral view   PA view

• Density
• Round or oval
• Sharp margins
• Homogenous density (exception: Air bronchogram in Lymphoma and Blastomycosis)
• No respect for anatomy (In cancer)
• Can break down leading to thick walled cavity
• May show calcification (Histoplasmoma, Tuberculoma, Hamartoma)

Note in gross cut section a mass which is well demarcated from the adjacent normal lung. Malignant tumors have infiltrating edges while benign tumors are rounded and well circumscribed.

Mass density can be encountered in 

• Lung cancer
• Benign tumors
• Sarcoma
• Lymphoma
• Wegners 
• Blastomycosis 
• Tuberculoma

Comprehend the following:

How would you radiologically distinguish Blastomycosis from lung cancer?

How would you radiologically distinguish Hamartoma from lung cancer?

What is your differential of a mass with air bronchogram?

What do you understand by the term " no respect for anatomy" ?